In advanced manufacturing of masks, there has been employed a technique that feeds back the quality of mask blanks being a material of the masks. For example, a method is known that performs pattern formation while avoiding a defective portion of a mask blank (see, e.g. Japanese Unexamined Patent Application Publication (JP-A) No. 2001-33941 (Patent Document 1)).
In order to perform such feedback, it is necessary to identify individual mask blanks. For this purpose, there have been proposed, for example, a mask blank formed with an identification marker for identifying or managing a mask blank glass substrate and a mask blank provided with an optically readable area code on an end face or the like of a mask blank glass substrate (see, e.g. Japanese Unexamined Patent Application Publication (JP-A) No. 2006-309143 (Patent Document 2)).